Tropical climates, which occur between 23°30'N and S latitude (Jacob 1988), encompass a wide variety of plant communities (Hartshorn 1983, 1988), many of which are diverse in their woody floras. Within this geographic region, temperature and the amount and seasonality of rainfall define habitat types (UNESCO 1978). The F AO has estimated that there 1 are about 19 million km of potentially forested area in the global tropics, of which 58% were estimated to still be in closed forest in the mid-1970s (Sommers 1976; UNESCO 1978). Of this potentially forested region, 42% is categorized as dry forest lifezone, 33% is tropical moist forest, and 25% is wet or rain forest (Lugo 1988). The species diversity of these tropical habitats is very high. Raven (1976, in Mooney 1988) estimated that 65% of the 250,000 or more plant species of the earth are found in tropical regions. Of this floristic assemblage, a large fraction are woody species. In the well-collected tropical moist forest of Barro Colorado Island, Panama, 39. 7% (481 of 1212 species) of the native phanerogams are woody, arborescent species (Croat 1978). Another 21. 9% are woody vines and lianas. Southeast Asian Dipterocarp forests may contain 120-200 species of trees per hectare (Whitmore 1984), and recent surveys in upper Amazonia re corded from 89 to 283 woody species ~ 10 cm dbh per hectare (Gentry 1988). Tropical communities thus represent a global woody flora of significant scope.

Air pollutants provide environmental conditions that drastically differ in many respects from those to which forest trees are naturally adapted. Leading experts in the field here consider these questions of immediate relevance arising from the changing environment: (1) Do air pollutants introduce effects of selection that differ from those known for populations that are not subject to such stress conditions? (2) If air pollutants introduce quantitatively or even qualitatively novel selective effects, which consequences might arise from the adaptation of forest tree populations to the present conditions as well as for the preservation of adaptability to future conditions? In addition to these questions, concepts for preservation of genetic resources are discussed.

The recent development of ideas on biodiversity conservation was already being considered almost three-quarters of a century ago for crop plants and the wild species related to them, by the Russian geneticist N.!. Vavilov. He was undoubtedly the first scientist to understand the impor tance for humankind of conserving for utilization the genetic diversity of our ancient crop plants and their wild relatives from their centres of diversity. His collections showed various traits of adaptation to environ mental extremes and biotypes of crop diseases and pests which were unknown to most plant breeders in the first quarter of the twentieth cen tury. Later, in the 1940s-1960s scientists began to realize that the pool of genetic diversity known to Vavilov and his colleagues was beginning to disappear. Through the replacement of the old, primitive and highly diverse land races by uniform modem varieties created by plant breed ers, the crop gene pool was being eroded. The genetic diversity of wild species was equally being threatened by human activities: over-exploita tion, habitat destruction or fragmentation, competition resulting from the introduction of alien species or varieties, changes and intensification of land use, environmental pollution and possible climate change.

Forest management must be sustainable not only in ecological, economic and social, but also genetic terms. Many forest managers are advocating and developing management strategies that give priority to conserving genetic diversity within production systems, or that recognise the importance of genetic considerations in achieving sustainable management. Forest Conservation Genetics draws together much previously uncollected information relevant to managing and conserving forests. The content emphasises the importance of conserving genetic diversity in achieving sustainable management. Each chapter is written by a leading expert and has been peer reviewed. Readers without a background in genetics will find the logical sequence of topics allows easy understanding of the principles involved and how those principles may impact on day-to-day forest planning and management decisions. The book is primarily aimed at undergraduate students of biology, ecology, forestry, and graduate students of forest genetics, resource management policy and/or conservation biology. It will prove useful for those teaching courses in these fields and as such help to increase the awareness of genetic factors in conservation and sustainable management, in both temperate and tropical regions.

This book, which contains 20 chapters, integrates the varied subdisciplines of genetics and their applications in gene conservation, tree improvement and biotechnology. Topics covered include: genetic variation in natural forests, the application of genetics in tree improvement and breeding programmes, and genomic sequences and molecular technologies. This book will be a valuable resource for students, scientists and professionals in the plant sciences, especially forest geneticists, tree breeders, forest managers and other natural resource specialists.

Issues concerning forest genetic diversity; Cases studies from IPGRI's research project; Lessons learned and applicability of reserch outcomes.

This book is a printed edition of the Special Issue "Genetics and Genomics of Forest Trees" that was published in Forests